Vitamin D: Sources and Health Effects

                                           Credit: Google Images

Contents

Vitamin D. 1

Sources of Vitamin D. 1

Functions of Vitamin D. 1

Effects of vitamin D deficiency. 2

Vitamin D toxicity. 2

 Vitamin D

Vitamin D, a fat soluble vitamin, is highly effective for bone health. It is also known as sunshine vitamin as it is produced in the body during sun light exposure.

Vitamin D is generally present in two dietary forms;

            D2 (ergocalciferol)

            D3 (cholecalciferol)

Vitamin D status of an individual is determined by measuring the serum levels of a vitamin D metabolite (25-hydroxyvitamin D or 25(OH)D) and it is examined that 20 ng/mL of this metabolite is required for healthy individuals (1).

Sources of Vitamin D

Vitamin D is endogenously synthesized when skin is exposed to ultraviolet B radiation and it fulfils 90% of vitamin D requirement.

Dietary sources of vitamin D include;

1.     Fish (tuna, sardines, salmon, herring, cod and mackerel)

2.     Egg yolk

3.     Beef liver

4.     Mushrooms

5.     Cod liver oil

6.     Milk

7.     Yogurt

8.     Cereals

9.     Orange juice

10.  Plant based drinks

In most cases, sun light exposure and diet are insufficient to cater vitamin D requirement therefore, vitamin D supplements are suggested. However, excessive supplementation can lead to vitamin D intoxication, so only use the supplements if prescribed by your physician (2).

Functions of Vitamin D

Vitamin D has various important functions, but few are well explored such as;

Maintenance and growth of bones: Vitamin D regulates the absorption of phosphorus and calcium from diet. These minerals are very important for bone health.

Regulation of immune system: Vitamin D is an important regulator of immune system and helps to improve immune function. Therefore, vitamin D deficiency is linked to various disorders.

                                             Credit: Google Images

Effects of vitamin D deficiency

Bone health

Vitamin D deficiency leads to osteoporosis (disease that causes bone weakness) and increases the frequency of falls or fractures. 

Fetal health

Vitamin D deficiency during pregnancy elevates the risk of preterm birth, gestational diabetes, deformation of fetal bones and pre-eclampsia (high blood pressure along with other kidney and liver problems) (1).

Tuberculosis (TB)

The positive correlation between TB and vitamin D level is also reported. A study described that ultraviolet B radiation therapy is useful against TB (4). However, vitamin D supplementation is not proven useful to improve the clinical outcomes of TB. Therefore, further intensive research is required to establish a strong link between vitamin D supplementation and TB treatment.

Respiratory tract infection

Research indicated that vitamin D deficient newborns (25(OH)D < 20 ng/mL) were at higher risk (6-fold) of developing respiratory syncytial virus-related bronchiolitis as compared to those with normal vitamin D levels. Moreover, vitamin D supplementation lowered the occurrence of acute respiratory tract infection (1).

In addition, vitamin D deficiency is also associated with higher incidence of hypertension, cancers, migraine, cardiovascular disorders and neuropsychiatric diseases including dementia, schizophrenia and depression (5). However, the evidence for vitamin D supplementation in preventing or treating these disorders is insufficient.

Vitamin D toxicity

Although, vitamin D is essential for proper functioning of body, inappropriate or chronic supplementation of vitamin D leads to various complications such as pain, bone demineralization, muscle weakness, polydipsia (excessive thirst) and nephrocalcinosis (calcium deposition in kidney) (1).

References

1.    1. Chang SW, Lee HC. Vitamin D and health-The missing vitamin in humans. Pediatrics & Neonatology. 2019 Jun 1;60(3):237-44.

2.     2. Benedik E. Sources of vitamin D for humans. International Journal for Vitamin and Nutrition Research. 2021 Oct 18.

3.     3. Bischoff-Ferrari HA, Dawson-Hughes B, Staehelin HB, Orav JE, Stuck AE, Theiler RO, Wong JB, Egli AN, Kiel DP, Henschkowski J. Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials. Bmj. 2009 Oct 1;339.

4.     4. Nnoaham KE, Clarke A. Low serum vitamin D levels and tuberculosis: a systematic review and meta-analysis. International journal of epidemiology. 2008 Feb 1;37(1):113-9.

5.     5. Weydert JA. Vitamin D in children’s health. Children. 2014 Sep 12;1(2):208-26.